11 May 2015

UK modified WinDRM

British Military/Government OFDM 51-tone modem, a odified WinDRM waveform with no evidence of the three Pilot Tones which are one of the WinDRM features. Parameters are Br 37.5, Sh 46.8, modulation is QAM and QPSK each two (Pic. 1). It is an "ON/OFF" system with 53.33 mSec periods (ACF of 106.66 mSec as shown in Pic. 2), in this sample no info is sent apparently during the ON (data) periods. It's clearly visible that the "ON" segments are sent using all the 51 channels and are interspersed alternatively by the subsets of odd and even channels (Pic. 3)